Idiopathic osteoporosis is a disease of unknown etiology characterized by progressive loss of bone mass and increased fragility, resulting in a marked increase in susceptibility to fractures. Osteoporosis is among the most prevalent of all musculoskeletal disorders, afflicting fifty six percent of women over 45 years of age. Praemer et al., “Musculoskeletal Conditions in the United States”, Amer. Acad. of Orthopaedic Surgeons, Park Ridge, Ill. (1992). Because its incidence increases with age and the percentage of elderly in the population is increasing, osteoporosis will become more common with time. Osteoporosis is difficult to treat locally, and there is presently no known cure. Finally, and most significantly, osteoporosis is associated with a substantial morbidity and mortality. The most serious fracture resulting from osteoporosis is that the of the proximal femur in the region of the hip joint. With an annual incidence of over 300,000, hip fractures are currently the most common fracture in the elderly. One out of every six Caucasian women will have a hip fracture during her lifetime (Cummings et al., Arch. Intern. Med., vol. 149, pp. 2455-2458 (1989)), and for those who attain the age of 90, this figure becomes one in three.
In addition to treating osteoporotic bone, a need exists for methods of treating or preventing osteoporosis related fractures, for example, by local administration of osteogenic proteins. Osteogenic proteins are those proteins capable of inducing, or assisting in the induction of, cartilage and/or bone formation. Many such osteogenic proteins have in recent years been isolated and characterized, and some have been produced by recombinant methods.
In addition, various formulations designed to deliver osteogenic proteins to a site where induction of bone formation is desired have been developed.
But despite substantial endeavors in this field, there remains a need for an effective method of repair and/or treatment of osteoporotic and osteopenic bone and for minimizing or reducing the incidence or severity of osteoporosis related fractures.